1. Field of the Invention
This invention relates to a backlash removing mechanism for removing backlash of a turning force transmitting system which includes a bevel gear wheel at an articulation section or an arm driving section of an industrial robot.
2. Description of the Prior Art
Generally, occurrence of backlash is a problem where a turning force transmitting system at an articulation section (wrist section or the like) or an arm driving section or the like of an industrial robot cannot employ, as a reduction gear, a reduction gear for a robot wherein the backlash is minimized or else employs a bevel gear mechanism other than a reduction gear in order to change the direction of operation. Particularly, a common gear mechanism involves a large backlash, and accordingly, a special measure is required to remove such a large backlash.
Thus, such a backlash removing mechanism for a rotational mechanical section including a bevel gear mechanism as shown in FIG. 5 is already known.
Referring to FIG. 5, a rotary shaft 41 is supported at an end portion thereof for rotation by means of a bearing 43 and has a bevel gear wheel 42 mounted at the end thereof. A rotational driving means such as a motor not shown is connected to the other end of the rotary shaft 41 so that the latter may be driven to rotate by the former. An output power shaft 44 is disposed perpendicularly to the rotary shaft 41 and supported for rotation by means of a bearing 45. Another bevel gear wheel 46 is mounted at an end of the output power shaft 44 and held in meshing engagement with the bevel gear 42 on the rotary shaft 41. The bevel gear wheel 46 is securely fastened to the output power shaft 44 by means of a plurality of bolts 48 with a liner 47 interposed therebetween for adjustment of a backlash between the bevel gear wheels 42 and 46.
Accordingly, a driving force from the rotational driving means not shown is transmitted to the perpendicularly extending output power shaft 44 by way of the rotary shaft 41 and bevel gear wheels 42 and 46.
In order to remove a possible backlash between the bevel gear wheels 42 and 46 of such a mechanism as described above, at first the bolts 48 are loosened, and then the bevel gear wheel 46 is moved in an axial upward or downward direction in FIG. 5 with respect to the bevel gear wheel 42 to adjust the thickness of the liner 47 or the number of such liners 47 between the bevel gear wheel 46 and the output power shaft 44 until a suitable position of the bevel gear wheel 46 is reached, whereafter the bolts 48 are tightened to secure the bevel gear wheel 46 again to the output power shaft 44.
Since generally the location at which the output power shaft 44 of the robot is to be disposed is determined in advance to a predetermined location and cannot be altered, it is impossible to move the output power shaft 44 itself in its axial direction (in the upward or downward direction in FIG. 5). Therefore, it is necessary to change the relative position of the bevel gear wheel 46 to the output power shaft 44 to adjust a backlash between the bevel gear wheels 42 and 46. Here, it is possible to employ a spline mechanism or a sliding key mechanism in order to fix the bevel gear wheel 46 in the rotational direction to the output power shaft 44 while permitting an axial movement of the bevel gear wheel 46 relative to the output power shaft 44. However, such mechanism is complicated, and besides such mechanism gives rise to another problem that it may probably involve a play.
For the reasons described just above, adjustment of a backlash is conventionally made by means of such a liner or liners 47 as described above.
The conventional backlash removing mechanism for an industrial robot described above, however, is disadvantageous in that much time is required for adjustment in thickness or number of such liner or liners 47 and re-adjustment of a backlash or maintenance of the mechanism due to abrasion of the bevel gear wheels 42 and 46 is cumbersome. Accordingly, improvement of such a conventional backlash removing mechanism as described above is expected.